Some currently existing methods of uniquely identifying items are based on overt or covert marks deliberately applied to items, usually by printing. Other methods rely on natural variations in a material substrate (fiber orientation in paper for example) to be used as a unique identifier. Current methods have significant deficiencies, however. These include the need to deliberately add overt or covert marks to the item in addition to any marks already present on the item for other purposes. The substrate variation method, for example, requires a specialized system that perceives the variations to be necessary. Also, for substrates that do not present a readily identifiable unique feature (some plastic films, for example) this method cannot be employed. These deficiencies seriously reduce the utility of these methods in the technical fields considered herein.